In vehicles, aircraft, telecommunications and other systems, batteries are often used to supply dc power to electrical devices (also referred to as electrical loads). The battery must be monitored to detect over voltage and low voltage conditions. An over voltage condition may be caused by electrical transients such as an electrostatic discharge, a charging system load dump, electrical noise, electromagnetic disturbances or a vehicle jump start may damage attached electrical loads. A low voltage condition may be caused, for example, by a fault in an electrical load drawing excessive amount of current, thereby reducing the battery's voltage. If a low voltage condition is detected, load shedding may be initiated by selective removal of one or more electrical loads to prevent the battery from being completely discharged. If an over voltage condition is detected, the battery voltage may be reduced to protect the electrical loads or the load may be temporarily disconnected from the vehicle battery.
In vehicles designed to tow trailers, a trailer tow connector and the electrical components installed in the vehicle to control trailer loads, are typically used to deliver electrical power to the trailer and may also monitor and control various devices or loads installed in the trailer. In production trailer tow designs, the electrical switching devices and circuit protection devices may be installed in several locations in the vehicle and are wired to the passive trailer tow connector. The trailer tow connector generally includes one or more output ports or pins adapted to deliver electrical power to the trailer devices or loads. The devices may include running lights, brake lights, parking lights, electric brakes, trailer battery and turn signals. Selected output ports or pins in the trailer tow connector are usually connected to a device that serves a particular purpose. For example, there may be an output port for operating the brake lights on the trailer and another output port for operating the right-hand turn signal and yet another for operating the left-hand turn signal.
Typically, a dedicated switched battery output pin on the trailer tow connector is used to power trailer loads which may include a trailer mounted battery or may directly power trailer mounted accessories. These trailer mounted accessories typically include the furnace/heater/refrigerator igniter circuits, the water system, a DC-AC inverter or trailer interior lighting. These trailer loads may be used while the trailer is being towed or when the tow vehicle is stationary, such as at a rest area or parked overnight. Additionally, the charging of the trailer battery is not controlled in production trailer tow electrical designs and a full charge current is constantly applied that can overheat and damage the trailer battery.
Existing trailer tow connectors with their supporting electronic switching and fixed protection devices typically lack the capability to intelligently perform real time measurements of the battery voltage to detect over voltage and low battery voltage conditions. Consequently, existing trailer tow connectors lack the capability to intelligently initiate load shedding to prevent complete depletion of the battery charge and also to reduce the output voltage, current or power delivered to prevent damage to the load. Furthermore, mechanical trailer tow connectors in use today include circuits that are powered by a vehicle battery (or other switched voltage applied) whenever the vehicle is running (switched battery output), or when the tow vehicle's headlamps, brakes, or turn signal outputs are active. These circuits remain powered even if a trailer is not connected to the tow vehicle, which may result in trailer tow connector reliability problems due to the voltage in the connector and its exposure to environmental extremes. Due to the voltage in the trailer tow connector, output pin corrosion and dendrite growth are frequent and can lead to undetected trailer electrical malfunctions.